The present invention relates to a device for rotating the polarization of a polarized electromagnetic wave at the exit from a waveguide. The device can be used in particular in a radiocommunications transceiver.
The polarization of an electromagnetic wave at the exit from a waveguide is usually rotated by means of a twist. FIG. 1 shows a twist known in the art. A twist TW is butt-jointed to the exit of a rectangular waveguide GO. The twist TW takes the form a rectangular section waveguide which is twisted about its longitudinal axis AL so that its entry cross-section S1 and its exit cross-section S2 are at a predefined angle xcex1 to each other which is equal to the required rotation angle. The entry cross-section of the twist S1 has the same dimensions as the cross-section of the waveguide GO.
One disadvantage of using a twist to rotate the polarization at the exit from a waveguide is the relatively large amount of space required to use a twist. It is generally necessary to integrate several twists into a radiocommunications transceiver unit. For example, there is one twist between the transmitter and the antenna, another between the receiver and the antenna and a third between the transmitter and the receiver. This rules out the production of a compact transceiver unit.
An object of the present invention is to remedy this disadvantage by proposing a device using the effects of electromagnetic coupling at the interface between the exit from a waveguide and the device of the invention. This coupling is obtained by geometrical characteristics of the interface between the device and the exit from the waveguide. It enables the polarization of an electromagnetic wave to be rotated without using a twist.
This object, together with others that become apparent hereinafter, is achieved by a device for rotating through a predefined angle the polarization of a polarized electromagnetic wave propagating in a first waveguide. The device comprises a second waveguide having a lateral port, the polarized electromagnetic wave propagates between a port of the first waveguide and the lateral port of the second waveguide via a coupling orifice that is smaller than the cross-section of the first waveguide and whose geometry is adapted to provide electromagnetic coupling between the first waveguide and the second waveguide, and the other port of the second waveguide is on a face perpendicular to the lateral port.
One advantage of the present invention is that it combines the effects of a bent waveguide changing the exit plane and a twist changing the polarization by carefully choosing the orientation of the second waveguide relative to the first waveguide.
The present invention also relates to a system for rotating the polarization of a polarized electromagnetic wave through a predefined angle, characterized in that it comprises a first waveguide connected to a second waveguide of a device according to claim 1 by a coupling orifice smaller than the cross-section of said first waveguide and whose geometry is adapted to provide electromagnetic coupling and in that the system includes a port in said first waveguide and a port in said second waveguide.
This invention is based on a priority application EP 00 44 0194 which is hereby incorporated by reference.